Facility report : ANSTO’s 6 MV NEC SIRIUS accelerator – an update since AMS 14 Ottawa

Abstract

ANSTO’s SIRIUS tandem accelerator is a customised 6 MV tandem accelerator manufactured by NEC and commissioned in 2015. It is a shared AMS and IBA instrument described in detail in Pastuovic et al (2015). Initial AMS performance data for cosmogenic isotopes 10Be, 26Al and 36Cl was presented at the Ottawa AMS14 Conference (Wilcken et al 2019). The AMS spectrometer consists of a 134 sample-wheel MC-SNICS Cs sputter source, a 45-degree spherical ESA (R=300 mm) and a double focusing insulated injection magnet (R=1000 mm, ME=20, vacuum gap = 70 mm). Two stripper gases (typically Ar and He) and thin foils are selectable in the terminal, and the selected charge state is focussed by an in tank electrostatic quadruple triplet positioned in the high energy column section. The high-energy section consists of two identical ME=176 analysing magnets (R=1270 mm) feeding two independent beam line transport systems, one for AMS and the other IBA. The AMS setup includes a post-stripper or energy degrader ladder, a 45-degree spherical ESA (R=3810 mm, gap = 30mm) and two magnetic quadrupoles. A choice of 3 AMS beam lines selectable by a ±30 degree switcher magnet provides options for dedicated radionuclide detection of 10Be (absorber cell), 36Cl and 26Al (multi-anode ionization counter), and an 8 m long TOF setup for future 129I and U-isotope measurements. A suite of sample geochemistry preparation laboratories, including a dedicated laboratory for preparation of in-situ 14C samples ( Fulop et al 2019) and an ice-core storage facility, provide AMS targets of 10Be (meteoric), 10Be, 26Al 14C and 36Cl (in-situ). The cosmogenic chemistry extraction laboratories host many visiting students and researchers to prepare samples and participate in AMS measurements. A wide variety of earth science applications in landscape evolution, sediment transport, tectonics, polar ice sheet stability, Quaternary geochronology supporting paleoclimate research change, solar variability and archaeology are supported. Ancillary facilities at ANSTO provide high precision elemental analyses (eg 9Be and 27Al) using a variety of techniques (ICP-OES, ICP-MS, AA, SEM, and XRF). We present details of recent data on routine AMS accelerator performance, reproducibility and linearity with various AMS standards, transmission, sample throughput, background reduction, and some improvements in sample chemistry methods.